<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8" />
  <title>js改变点位</title>
  <link rel="icon" href="https://img.kaikeba.com/kkb_portal_icon.ico">
  <style>
    body {
      margin: 0;
      overflow: hidden;
    }

    #canvas {
      background-color: antiquewhite;
    }
  </style>
</head>

<body>
  <canvas id="canvas"></canvas>
  <!-- 顶点着色器 -->
  <script id="vertexShader" type="x-shader/x-vertex">
      attribute vec4 a_Position;
      void main(){
          //点位
          gl_Position=a_Position;
          //尺寸
          gl_PointSize=50.0;
      }
    </script>
  <!-- 片元着色器 -->
  <script id="fragmentShader" type="x-shader/x-fragment">
      void main(){
          gl_FragColor=vec4(1,1,0,1);
      }
    </script>
  <script type="module">
    import { initShaders } from "../jsm/Utils.js";

    const canvas = document.querySelector("#canvas");
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;

    // 获取着色器文本
    const vsSource = document.querySelector("#vertexShader").innerText;
    const fsSource = document.querySelector("#fragmentShader").innerText;

    //三维画笔
    const gl = canvas.getContext("webgl");

    //初始化着色器
    initShaders(gl, vsSource, fsSource);

    //声明颜色 rgba
    gl.clearColor(0, 0, 0, 1);
    //刷底色
    gl.clear(gl.COLOR_BUFFER_BIT);

    //设置attribute 变量
    // a_Position=vec4(1,0,0,1)
    const a_Position = gl.getAttribLocation(gl.program, "a_Position");

    //修改attribute 变量
    // gl.vertexAttrib3f(a_Position, 0, 1, 0);
    // gl.vertexAttrib2f(a_Position, 0.5, 0.5);
    gl.vertexAttrib1f(a_Position, 0.1);

    //绘制顶点
    gl.drawArrays(gl.POINTS, 0, 1);
  </script>
</body>

</html>